Weight Loss May Lower Breast Cancer Risk in Older Women

Weight loss in postmenopausal women could reduce their odds of developing breast cancer, researchers have found. The study was published in the journal Cancer. 

Researchers assessed 61,335 postmenopausal women with no history of breast cancer and a normal mammogram. They measured the women’s body mass index (BMI) at baseline and after three years. At year three, changes in weight were categorized as stable (< 5%), loss (≥ 5%), or gain (≥ 5%). Weight loss intentionality was self-reported. 

At follow-up (mean 11.4 years), there had been 3,061 incident breast cancers. The weight loss group (n = 8,175) had a significantly reduced risk of breast cancer compared to the stable cohort (n = 41,139) (hazard ratio [HR], 0.88; 95% confidence interval [CI], 0.78‐0.98; P = 0.02). Researchers observed no significant difference when adjusting for mammography (HR, 0.88; 95% CI, 0.78‐0.99) or whether or not weight loss was intentional. Women who gained weight (n = 12,021) did not have a higher risk of breast cancer (HR, 1.02; 95% CI, 0.93‐1.11) but did have a higher incidence of triple‐negative breast cancer (HR, 1.54; 95% CI, 1.16‐2.05). 

“Our study indicates that moderate, relatively short-term weight reduction was associated with a statistically significant reduction in breast cancer risk for postmenopausal women,” said study author Rowan Chlebowski, MD, PhD, of the City of Hope National Medical Center. “These are observational results, but they are also supported by randomized clinical trial evidence from the Women’s Health Initiative Dietary Modification trial where, in a randomized clinical trial setting, adopting a low-fat dietary pattern that was associated with a similar magnitude of weight loss resulted in a significant improvement in breast cancer overall survival. These findings, taken together, provide strong correlative evidence that a modest weight loss program can impact breast cancer.” 

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